The present invention relates to an arrangement for controlling the amplitude of an electric signal for a digital electronic apparatus, comprising a generator of a first logical signal of constant amplitude and of a frequency comprised within a predetermined frequency band, and a utilizing device sensitive to the amplitude of the signal.
This invention also relates to a method of controlling the amplitude of an electric signal in a digital environment, wherein a first logical signal is generated at constant amplitude and at low frequency.
More particularly, the invention relates to the control of the volume of an acoustic signalling device used in a digital desk-top apparatus for office use, such as a personal computer, a data processing work station or a telephone exchange.
As is known, modern digital desk-top apparatus includes sound generating circuitry which is able, under the control of a processor, to generate electric signals of any form, periodical or not, which are then translated into acoustic signals by a loudspeaker. Many application programs in the field of computers utilize the capacity to generate and disseminate sounds, whether as a simple signal attracting the attention of the operator in accordance with the program being executed, or for generating musical themes or tunes, or for synthesizing words and phrases of human speech.
For the purpose of adapting the volume of the sound to given surroundings or requirements, it has already been proposed to effect "static adjustment" of the volume of the sound by means of a device adjustable from time to time by a manupulation performed by the operator. Normally, such adjustment is effected by connecting in the circuit a potentiometer accessible to the operator and adapted to cut down the electric power carried to the loudspeaker, so that the command is of analog type.
However, these known adjusting devices have the disadvantage of not allowing integration with the digital circuits both of the computer and of the acoustic signals generator. Moreover, these adjusting devices do not allow ready automatic or programmed actuation for achieving "dynamic adjustment" of the volume, as may be required, for example, in line with processing results or the background noise of the environment or, in the case of a text-to-speech translator, for introducing an expressive modulation or a modulation of inflexion of the sound in accordance with the context of the talk.